Improve block body's diagnostics

dev_tests/src/verify_expr.rs

@@ -16,45 +16,40 @@ use rottlib::parser::Parser;
 /// Keep these small: the goal is to inspect lexer diagnostics and delimiter
 /// recovery behavior, not full parser behavior.
 const TEST_CASES: &[(&str, &str)] = &[
-    // L0001: invalid or unknown token
+    // P0027: `else` without a matching `if`
-    (
-        "files/L0001_01.uc",
-        "`",
-    ),
-
-    // L0002: unexpected closing delimiter
-    (
-        "files/L0002_01.uc",
-        "]",
-    ),
-
-    // L0003: unclosed delimiter before later closing delimiter
     //
-    // The `}` can still recover by matching the earlier `{`.
+    // `else` cannot start a standalone block item. The parser should report
+    // P0027 at `else`, then recover by bailing out of the current block.
     (
-        "files/L0003_01.uc",
+        "files/P0027_01.uc",
-        "{\n    foo(\n}\n",
+        "{\n    local bool bReady;\n    bReady = CheckReady();\n    else { StartMatch(); }\n    NotifyReady();\n}\n",
     ),
 
-    // L0004: mismatched closing delimiter
+    // P0027: `case` outside of a `switch`
-    (
-        "files/L0004_01.uc",
-        "(]",
-    ),
-
-    // L0005: unclosed delimiter at end of file
-    (
-        "files/L0005_01.uc",
-        "foo(",
-    ),
-
-    // Mixed recovery case:
     //
-    // `)` recovers by matching `(` after treating `[` as unclosed;
+    // `case` is a switch-arm boundary, not a valid statement or expression
-    // the following `]` is then unexpected.
+    // starter in an ordinary block.
     (
-        "files/L_mixed_01.uc",
+        "files/P0027_02.uc",
-        "([)]",
+        "{    local int Count;    Count = 3;    case 3:        Count++;    UpdateHud();}",
+    ),
+
+    // P0027: standalone `until` without a preceding `do`
+    //
+    // `until` is only meaningful as the tail of `do ... until`, so it should
+    // not be accepted as a normal block item.
+    (
+        "files/P0027_03.uc",
+        "{\n    local bool bDone;\n    bDone = false;\n    until (bDone)\n    TickWork();\n}\n",
+    ),
+
+    // P0027: preprocessor/exec directive inside a statement block
+    //
+    // `#exec` is declaration/top-level-like syntax, not a valid statement or
+    // expression inside a braced statement block.
+    (
+        "files/P0027_04.uc",
+        "{\n    local int Count;\n    Count = 0;\n    #exec TEXTURE IMPORT NAME=Bad FILE=Bad.bmp\n    Count++;\n}\n",
     ),
 ];
 
@@ -62,12 +57,12 @@ const TEST_CASES: &[(&str, &str)] = &[
 ///
 /// For lexer-focused fixtures this is usually noisy, so keep it off unless you
 /// want to inspect how parser recovery behaves after lexer diagnostics.
-const RUN_PARSER: bool = false;
+const RUN_PARSER: bool = true;
 
 /// If true, print the parsed expression using Debug formatting.
 const PRINT_PARSED_EXPR: bool = false;
 
-/// If true, print diagnostics even when parsing returned a value.
+const PRINT_LEXER_DIAGNOSTICS: bool = false;
 const ALWAYS_PRINT_DIAGNOSTICS: bool = true;
 
 fn main() {
@@ -89,7 +84,7 @@ fn main() {
         } else {
             had_any_problem = true;
 
-            if ALWAYS_PRINT_DIAGNOSTICS {
+            if PRINT_LEXER_DIAGNOSTICS {
                 println!("Lexer diagnostics:");
                 for diag in lexer_diagnostics {
                     render_diagnostic(diag, &tf, Some(label), false);

rottlib/src/diagnostics/parse_error_diagnostics/block_items.rs

@@ -0,0 +1,111 @@
+use super::{Diagnostic, DiagnosticBuilder, FoundAt, found_at};
+use crate::lexer::{Token, TokenSpan, TokenizedFile};
+use crate::parser::ParseError;
+
+/// P0025
+pub(super) fn diagnostic_block_missing_semicolon_after_expression<'src>(
+    error: ParseError,
+    file: &TokenizedFile<'src>,
+) -> Diagnostic {
+    let expression_span = error.related_spans.get("expression_span").copied();
+
+    let primary_span = TokenSpan::new(error.blame_span.end);
+
+    let primary_text = match found_at(file, primary_span.end) {
+        FoundAt::Token(token_text) => format!("expected `;` before `{}`", token_text),
+        FoundAt::EndOfFile => "expected `;` before end of file".to_string(),
+        FoundAt::Unknown => "expected `;` here".to_string(),
+    };
+
+    let mut builder = DiagnosticBuilder::error("missing `;` after expression statement");
+
+    if let Some(expression_span) = expression_span {
+        if file.same_line(expression_span.start, primary_span.end) {
+            builder = builder.secondary_label(expression_span, "expression statement");
+        } else {
+            builder = builder.secondary_label(
+                TokenSpan::new(expression_span.end),
+                "expression statement ends here",
+            );
+        }
+    }
+
+    builder
+        .primary_label(primary_span, primary_text)
+        .code("P0025")
+        .build()
+}
+
+/// P0026
+pub(super) fn diagnostic_block_missing_closing_brace<'src>(
+    error: ParseError,
+    file: &TokenizedFile<'src>,
+) -> Diagnostic {
+    let left_brace_span = error.related_spans.get("left_brace").copied();
+    let unexpected_token_span = error.related_spans.get("unexpected_token").copied();
+
+    let (mut primary_span, primary_text) =
+        if let Some(unexpected_token_span) = unexpected_token_span {
+            let primary_span = TokenSpan::new(unexpected_token_span.end);
+
+            let primary_text = match found_at(file, primary_span.end) {
+                FoundAt::Token(token_text) => format!("expected `}}` before `{}`", token_text),
+                FoundAt::EndOfFile => "expected `}` before end of file".to_string(),
+                FoundAt::Unknown => "expected `}` here".to_string(),
+            };
+
+            (primary_span, primary_text)
+        } else {
+            (
+                TokenSpan::new(error.blame_span.end),
+                "expected `}` before end of file".to_string(),
+            )
+        };
+
+    let builder = DiagnosticBuilder::error("missing `}` to close block");
+
+    if let Some(left_brace_span) = left_brace_span
+        && !file.same_line(left_brace_span.start, primary_span.end)
+    {
+        primary_span.start = left_brace_span.start;
+    }
+
+    builder
+        .primary_label(primary_span, primary_text)
+        .code("P0026")
+        .build()
+}
+
+/// P0027
+pub(super) fn diagnostic_block_expected_item<'src>(
+    error: ParseError,
+    file: &TokenizedFile<'src>,
+) -> Diagnostic {
+    let primary_span = error.blame_span;
+
+    let (title, primary_text) = match file.token_at(primary_span.start).map(|data| data.token) {
+        Some(Token::ExecDirective) => (
+            "expected statement or expression, found `#exec` directive".to_string(),
+            "`#exec` directives are not allowed in a statement block".to_string(),
+        ),
+        _ => match found_at(file, primary_span.start) {
+            FoundAt::Token(token_text) => (
+                format!("expected statement or expression, found `{}`", token_text),
+                format!("unexpected `{}`", token_text),
+            ),
+            FoundAt::EndOfFile => (
+                "expected statement or expression, found end of file".to_string(),
+                "reached end of file here".to_string(),
+            ),
+            FoundAt::Unknown => (
+                "expected statement or expression".to_string(),
+                "expected statement or expression here".to_string(),
+            ),
+        },
+    };
+
+    DiagnosticBuilder::error(title)
+        .primary_label(primary_span, primary_text)
+        .code("P0027")
+        .build()
+}

rottlib/src/diagnostics/parse_error_diagnostics/control_flow_expressions.rs

@@ -263,7 +263,7 @@ pub(super) fn diagnostic_for_each_iterator_expression_expected<'src>(
     let control_keyword_text = control_keyword_span.and_then(|span| file.token_text(span.end));
 
     let found = found_at(file, error.blame_span.end);
-    let found_body_block_start = matches!(found, FoundAt::Token("{"));
+    let _ = matches!(found, FoundAt::Token("{"));
 
     let (header_text, primary_text) = match (control_keyword_text, found) {
         (Some(keyword_text), FoundAt::Token(token_text)) => {

rottlib/src/diagnostics/parse_error_diagnostics/mod.rs

@@ -10,9 +10,14 @@
 //! parser areas or grammar families.
 
 use super::{Diagnostic, DiagnosticBuilder};
+use crate::diagnostics::parse_error_diagnostics::block_items::{
+    diagnostic_block_expected_item, diagnostic_block_missing_closing_brace,
+    diagnostic_block_missing_semicolon_after_expression,
+};
 use crate::lexer::{TokenPosition, TokenSpan, TokenizedFile};
 use crate::parser::{ParseError, ParseErrorKind};
 
+mod block_items;
 mod control_flow_expressions;
 mod primary_expressions;
 
@@ -133,6 +138,14 @@ pub(crate) fn diagnostic_from_parse_error<'src>(
         }
         ParseErrorKind::BreakValueInvalidStart => diagnostic_break_value_invalid_start(error, file),
         ParseErrorKind::GotoMissingLabel => diagnostic_goto_missing_label(error, file),
+        // block_items.rs
+        ParseErrorKind::BlockMissingSemicolonAfterExpression => {
+            diagnostic_block_missing_semicolon_after_expression(error, file)
+        }
+        ParseErrorKind::BlockMissingClosingBrace => {
+            diagnostic_block_missing_closing_brace(error, file)
+        }
+        ParseErrorKind::BlockExpectedItem => diagnostic_block_expected_item(error, file),
 
         _ => DiagnosticBuilder::error(format!("error {:?} while parsing", error.kind))
             .primary_label(error.covered_span, "happened here")

rottlib/src/lexer/raw_lexer.rs

@@ -59,7 +59,7 @@ pub enum BraceKind {
 #[logos(extras = LexerState)]
 pub enum RawToken {
     // # Compiler/directive keywords
-    #[regex(r"(?i)#exec[^\r\n]*(?:\r\n|\n|\r)?")]
+    #[regex(r"(?i)#exec[^\r\n]*")]
     ExecDirective,
     #[regex("(?i)cpptext", |lex| {
         if is_next_nontrivia_left_brace(lex) {

rottlib/src/parser/cursor.rs

@@ -364,6 +364,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
     }
 
     /// Ensures that parsing has advanced past `old_position`. 
+    // TODO: must be given peeked value!
     ///
     /// This is intended as a safeguard against infinite-loop bugs while
     /// recovering from invalid input. In debug builds it asserts that progress

rottlib/src/parser/errors.rs

@@ -64,6 +64,12 @@ pub enum ParseErrorKind {
     BreakValueInvalidStart,
     /// P0024
     GotoMissingLabel,
+    /// P0025
+    BlockMissingSemicolonAfterExpression,
+    /// P0026
+    BlockMissingClosingBrace,
+    /// P0027
+    BlockExpectedItem,
     // ================== Old errors to be thrown away! ==================
     /// Expression inside `(...)` could not be parsed and no closing `)`
     /// was found.
@@ -83,11 +89,7 @@ pub enum ParseErrorKind {
 
     TypeSpecClassMissingInnerType,
     TypeSpecClassMissingClosingAngle,
-    /// An expression inside a block is not terminated with `;`.
-    BlockMissingSemicolonAfterExpression,
-    /// A statement inside a block is not terminated with `;`.
     BlockMissingSemicolonAfterStatement,
-    BlockMissingClosingBrace,
     /// `switch` has no body (missing matching braces).
     SwitchMissingBody,
     /// The first top-level item in a `switch` body is not a `case`.

rottlib/src/parser/grammar/class.rs

@@ -357,7 +357,7 @@ impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
                 Ok(rule) => rules.push(rule),
                 Err(error) => {
                     self.report_error(error);
-                    self.recover_until(SyncLevel::Statement);
+                    self.recover_until(SyncLevel::StatementStart);
                     let _ = self.eat(Token::Semicolon);
                     if !self.ensure_progress_or_break(loop_start) {
                         break;
@@ -899,7 +899,7 @@ impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
                 }
                 Some((_, _)) if declarators.is_empty() => {
                     self.report_error_here(ParseErrorKind::DeclBadVariableIdentifier);
-                    self.recover_until(SyncLevel::Statement);
+                    self.recover_until(SyncLevel::StatementStart);
                     let _ = self.eat(Token::Semicolon);
                     break;
                 }

rottlib/src/parser/grammar/declarations/enum_definition.rs

@@ -104,7 +104,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
         variants: &mut ArenaVec<'arena, IdentifierToken>,
     ) -> ControlFlow<()> {
         self.parse_identifier(ParseErrorKind::EnumBadVariant)
-            .sync_error_until(self, SyncLevel::Statement)
+            .sync_error_until(self, SyncLevel::StatementStart)
             .ok_or_report(self)
             .map_or(ControlFlow::Break(()), |variant| {
                 variants.push(variant);
@@ -122,7 +122,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
         let Some(variant) = self
             .parse_identifier(ParseErrorKind::EnumBadVariant)
             .widen_error_span_from(error_start_position)
-            .sync_error_until(self, SyncLevel::Statement)
+            .sync_error_until(self, SyncLevel::StatementStart)
             .ok_or_report(self)
         else {
             // If we don't even get a good identifier - error is different

rottlib/src/parser/grammar/declarations/struct_definition.rs

@@ -93,7 +93,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
                 self.advance();
                 if !self.eat(Token::CppBlock) {
                     self.report_error_here(ParseErrorKind::CppDirectiveMissingCppBlock);
-                    self.recover_until(SyncLevel::Statement);
+                    self.recover_until(SyncLevel::StatementStart);
                 }
                 StructBodyItemParseOutcome::Skip
             }

rottlib/src/parser/grammar/declarations/variable_declarators.rs

@@ -104,7 +104,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
     ) -> ControlFlow<()> {
         if let Some(parsed_declarator) = self
             .parse_variable_declarator()
-            .sync_error_until(self, SyncLevel::Statement)
+            .sync_error_until(self, SyncLevel::StatementStart)
             .ok_or_report(self)
         {
             declarators.push(parsed_declarator);
@@ -122,7 +122,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
         if let Some(parsed_declarator) = self
             .parse_variable_declarator()
             .widen_error_span_from(error_start_position)
-            .sync_error_until(self, SyncLevel::Statement)
+            .sync_error_until(self, SyncLevel::StatementStart)
             .ok_or_report(self)
         {
             self.make_error_at_last_consumed(ParseErrorKind::DeclNoSeparatorBetweenVariableDeclarations)

rottlib/src/parser/grammar/expression/block.rs

@@ -4,106 +4,187 @@
 //! function, loop, state, and similar constructs after the opening `{`
 //! has been consumed.
 
-use crate::arena::ArenaVec;
+use crate::ast::{BlockBody, Expression, ExpressionRef, Statement, StatementList, StatementRef};
-use crate::ast::{BlockBody, Expression, ExpressionRef, Statement, StatementRef};
 use crate::lexer::{Token, TokenPosition, TokenSpan};
-use crate::parser::{ParseErrorKind, Parser};
+use crate::parser::{ParseErrorKind, ParseResult, Parser, ResultRecoveryExt, SyncLevel};
 
 impl<'src, 'arena> Parser<'src, 'arena> {
-    /// Parses a `{ ... }` block after the opening `{` has been consumed.
+    /// Parses a braced block body into an [`Expression::Block`].
     ///
-    /// Consumes tokens until the matching `}` and returns an
+    /// The opening `{` must already have been consumed. The returned block's
-    /// [`Expression::Block`] whose span covers the entire block, from
+    /// span covers the whole block, from `left_brace_position` through
-    /// `opening_brace_position` to the closing `}`.
+    /// the closing `}`.
     ///
-    /// On premature end-of-file, returns a best-effort block.
+    /// On premature end-of-file, reports the missing `}` and returns
+    /// a best-effort block.
     #[must_use]
-    pub(crate) fn parse_block_tail(
+    pub(crate) fn parse_block_body_tail(
         &mut self,
-        opening_brace_position: TokenPosition,
+        left_brace_position: TokenPosition,
     ) -> ExpressionRef<'src, 'arena> {
         let BlockBody { statements, span } =
-            self.parse_braced_block_statements_tail(opening_brace_position);
+            self.parse_braced_block_statements_tail(left_brace_position);
         self.arena.alloc_node(Expression::Block(statements), span)
     }
 
-    /// Parses a `{ ... }` block after the opening `{` has been consumed.
+    /// Parses the statements in a braced block body.
     ///
-    /// Consumes tokens until the matching `}` and returns the contained
+    /// The opening `{` must already have been consumed. Returns the parsed
-    /// statements together with a span that covers the entire block, from
+    /// statements and a span covering the whole block, from
-    /// `opening_brace_position` to the closing `}`.
+    /// `left_brace_position` through the closing `}`.
     ///
-    /// On premature end-of-file, returns a best-effort statement list and span.
+    /// On premature end-of-file, reports the missing `}` and returns
+    /// a best-effort body.
     #[must_use]
     pub(crate) fn parse_braced_block_statements_tail(
         &mut self,
-        opening_brace_position: TokenPosition,
+        left_brace_position: TokenPosition,
     ) -> BlockBody<'src, 'arena> {
         let mut statements = self.arena.vec();
         while let Some((token, token_position)) = self.peek_token_and_position() {
             if token == Token::RightBrace {
                 self.advance(); // '}'
-                let span = TokenSpan::range(opening_brace_position, token_position);
+                let span = TokenSpan::range(left_brace_position, token_position);
                 return BlockBody { statements, span };
             }
-            self.parse_next_block_item_into(&mut statements);
+            match self.parse_and_append_next_block_item(&mut statements) {
+                Ok(()) => {
+                    // Guard against parser bugs that would otherwise leave
+                    // block parsing stuck on the same token.
                     self.ensure_forward_progress(token_position);
                 }
-        // Reached EOF without a closing `}`
+                Err(error) => {
-        self.report_error_here(ParseErrorKind::BlockMissingClosingBrace);
+                    // Item-level recovery failed,
+                    // so escalate to the block boundary.
+                    let error = error.sync_error_at_matching_delimiter(self, left_brace_position);
+                    let error_statement = error.fallback(self);
+                    statements.push(error_statement);
                     let span = TokenSpan::range(
-            opening_brace_position,
+                        left_brace_position,
                         self.last_consumed_position_or_start(),
                     );
+                    return BlockBody { statements, span };
+                }
+            }
+        }
+        let eof_position = self.peek_position_or_eof();
+        self.make_error_at(ParseErrorKind::BlockMissingClosingBrace, eof_position)
+            .related_token("left_brace", left_brace_position)
+            .report(self);
+        let span = TokenSpan::range(left_brace_position, self.last_consumed_position_or_start());
+
         BlockBody { statements, span }
     }
 
-    /// Parses one statement inside a `{ ... }` block and appends it to
+    /// Parses one statement-like item inside a `{ ... }` block and appends it
-    /// `statements`.
+    /// to `statements`.
     ///
     /// This method never consumes the closing `}` and is only meant to be
-    /// called while parsing inside a block. It always appends at least one
+    /// called while parsing inside a block.
-    /// statement, even in the presence of syntax errors.
+    ///
-    pub(crate) fn parse_next_block_item_into(
+    /// On success, it appends exactly one statement. If neither a statement nor
+    /// an expression statement can be recovered locally, it returns
+    /// an unreported error so the enclosing block parser can recover at
+    /// block level.
+    pub(crate) fn parse_and_append_next_block_item(
         &mut self,
-        statements: &mut ArenaVec<'arena, StatementRef<'src, 'arena>>,
+        statements: &mut StatementList<'src, 'arena>,
-    ) {
+    ) -> ParseResult<'src, 'arena, ()> {
-        let mut next_statement = self.parse_statement().unwrap_or_else(|| {
+        let mut statement = match self.parse_statement() {
-            let next_expression = self.parse_expression();
+            Some(statement) => statement,
-            let next_expression_span = *next_expression.span();
+            None => {
-            self.arena
+                // Non-statement starters are parsed as expression statements
-                .alloc_node(Statement::Expression(next_expression), next_expression_span)
+                self.parse_expression_statement_in_block()?
-        });
+            }
-        if statement_needs_semicolon(&next_statement)
+        };
-            && let Some((Token::Semicolon, semicolon_position)) = self.peek_token_and_position()
+        if block_item_requires_semicolon(&statement) {
-        {
+            match self.peek_token_and_position() {
-            next_statement.span_mut().extend_to(semicolon_position);
+                Some((Token::Semicolon, semicolon_position)) => {
+                    statement.span_mut().extend_to(semicolon_position);
                     self.advance(); // ';'
                 }
-        statements.push(next_statement);
+                // A final expression before `}` may omit `;`; this makes it
-    }
+                // the block's tail value.
-}
+                //
-
+                // On end-of-file, suppress the missing-`;` diagnostic as well.
-fn statement_needs_semicolon(statement: &Statement) -> bool {
+                // The block parser will report the missing `}`,
-    use Statement::{Empty, Error, Expression, Function, Label, LocalVariableDeclaration};
+                // and an extra semicolon error would just cascade.
-    match statement {
+                None | Some((Token::RightBrace, _)) => (),
-        Empty | Label(_) | Error | Function(_) => false,
+                Some((_, unexpected_token_position)) => {
-        Expression(expression) => expression_needs_semicolon(expression),
+                    self.make_error_at_last_consumed(
-        LocalVariableDeclaration { .. } => true,
+                        ParseErrorKind::BlockMissingSemicolonAfterExpression,
-    }
-}
-
-const fn expression_needs_semicolon(expression: &Expression) -> bool {
-    use Expression::{Block, DoUntil, Error, For, ForEach, If, Switch, While};
-    matches!(
-        expression,
-        Block { .. }
-            | If { .. }
-            | While { .. }
-            | DoUntil { .. }
-            | ForEach { .. }
-            | For { .. }
-            | Switch { .. }
-            | Error
                     )
+                    .widen_error_span_from(statement.span().start)
+                    .blame_token(unexpected_token_position)
+                    .related("expression_span", *statement.span())
+                    .report(self);
+                }
+            }
+        }
+        statements.push(statement);
+        Ok(())
+    }
+
+    fn parse_expression_statement_in_block(
+        &mut self,
+    ) -> ParseResult<'src, 'arena, StatementRef<'src, 'arena>> {
+        let expression_start_position = self.peek_position_or_eof();
+        let expected_block_item_after_position = self.last_consumed_position_or_start();
+        let expression_result = self.parse_expression_with_start_error(
+            ParseErrorKind::BlockExpectedItem,
+            expected_block_item_after_position,
+            expected_block_item_after_position,
+        );
+        let expression = match expression_result {
+            Ok(expression) => expression,
+            Err(error) => {
+                let expression_recovery_made_no_progress =
+                    self.peek_position_or_eof() == expression_start_position;
+                // Without progress, a fallback statement could leave
+                // the block loop stuck.
+                if expression_recovery_made_no_progress {
+                    return self.recover_bad_block_item_start_as_error_statement(error);
+                }
+                error.fallback(self)
+            }
+        };
+        let expression_span = *expression.span();
+        Ok(self
+            .arena
+            .alloc_node(Statement::Expression(expression), expression_span))
+    }
+
+    fn recover_bad_block_item_start_as_error_statement(
+        &mut self,
+        error: crate::parser::ParseError,
+    ) -> ParseResult<'src, 'arena, StatementRef<'src, 'arena>> {
+        let position_before_statement_recovery = self.peek_position_or_eof();
+        // Recover one damaged block item if possible;
+        // otherwise let the enclosing block recover at its own boundary.
+        let error = error.sync_error_at(self, SyncLevel::StatementTerminator);
+        if self.peek_position_or_eof() != position_before_statement_recovery {
+            return Ok(error.fallback(self));
+        }
+        Err(error)
+    }
+}
+
+fn block_item_requires_semicolon(statement: &Statement) -> bool {
+    // Control-flow and block expressions do not require a trailing semicolon
+    // when used as block items.
+    if let Statement::Expression(expression) = statement {
+        !matches!(
+            **expression,
+            Expression::Block { .. }
+                | Expression::If { .. }
+                | Expression::While { .. }
+                | Expression::DoUntil { .. }
+                | Expression::ForEach { .. }
+                | Expression::For { .. }
+                | Expression::Switch { .. }
+                | Expression::Error
+        )
+    } else {
+        false
+    }
 }

rottlib/src/parser/grammar/expression/primary/mod.rs

@@ -78,7 +78,7 @@ impl<'src, 'arena> Parser<'src, 'arena> {
                 token_position,
             ),
             Token::LeftParenthesis => self.parse_parenthesized_expression_tail(token_position),
-            Token::LeftBrace => self.parse_block_tail(token_position),
+            Token::LeftBrace => self.parse_block_body_tail(token_position),
             Token::Keyword(keyword) => {
                 match self.try_parse_keyword_primary(keyword, token_position) {
                     Some(keyword_expression) => keyword_expression,

rottlib/src/parser/grammar/expression/switch.rs

@@ -96,7 +96,7 @@ impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
             // at statement sync level.
             self.expect(Token::Colon, ParseErrorKind::SwitchCaseMissingColon)
                 .widen_error_span_from(case_position)
-                .sync_error_until(self, crate::parser::SyncLevel::Statement)
+                .sync_error_until(self, crate::parser::SyncLevel::StatementStart)
                 .report_error(self);
         }
         let mut body = self.arena.vec();
@@ -115,7 +115,7 @@ impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
         self.advance(); // 'default'
         self.expect(Token::Colon, ParseErrorKind::SwitchCaseMissingColon)
             .widen_error_span_from(default_position)
-            .sync_error_until(self, crate::parser::SyncLevel::Statement)
+            .sync_error_until(self, crate::parser::SyncLevel::StatementStart)
             .report_error(self);
         self.parse_switch_arm_body(statements);
     }
@@ -129,7 +129,7 @@ impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
             match token {
                 Token::Keyword(Keyword::Case | Keyword::Default) | Token::RightBrace => break,
                 _ => {
-                    self.parse_next_block_item_into(statements);
+                    self.parse_and_append_next_block_item(statements);
                     self.ensure_forward_progress(token_position);
                 }
             }

rottlib/src/parser/grammar/statement.rs

@@ -11,8 +11,9 @@ impl<'src, 'arena> crate::parser::Parser<'src, 'arena> {
     /// Parses a single statement.
     ///
     /// Does not consume a trailing `;` except for [`Statement::Empty`].
-    /// The caller handles semicolons. Returns [`Some`] if a statement is
+    /// The caller handles semicolons (WRONG NOW - WE MUST HANDLE THEM). Returns [`Some`] if a statement is
     /// recognized; otherwise [`None`].
+    /// ALSO WE SPECIFICALLY DONT HANDLE EXPRESSION TYPE STATEMENTS
     #[must_use]
     pub(crate) fn parse_statement(&mut self) -> Option<StatementRef<'src, 'arena>> {
         let Some((token, lexeme, position)) = self.peek_token_lexeme_and_position() else {

rottlib/src/parser/recovery.rs

@@ -50,7 +50,10 @@ pub enum SyncLevel {
     ///
     /// Includes `;` and keywords that begin standalone statements /
     /// statement-like control-flow forms.
-    Statement,
+    StatementStart,
+
+    /// Statement terminator `;`.
+    StatementTerminator,
 
     /// Start of a `switch` arm.
     ///
@@ -77,7 +80,7 @@ impl SyncLevel {
         use crate::lexer::Keyword;
         use SyncLevel::{
             BlockBoundary, CloseAngleBracket, CloseBracket, CloseParenthesis, DeclarationStart,
-            ExpressionStart, ListSeparator, Statement, SwitchArmStart,
+            ExpressionStart, ListSeparator, StatementStart, StatementTerminator, SwitchArmStart,
         };
 
         match token {
@@ -88,8 +91,7 @@ impl SyncLevel {
             Token::RightBracket => Some(CloseBracket),
 
             // Statement-level boundaries
-            Token::Semicolon
+            Token::Keyword(
-            | Token::Keyword(
                 Keyword::If
                 | Keyword::Else
                 | Keyword::Switch
@@ -102,7 +104,9 @@ impl SyncLevel {
                 | Keyword::Break
                 | Keyword::Continue
                 | Keyword::Local,
-            ) => Some(Statement),
+            ) => Some(StatementStart),
+
+            Token::Semicolon => Some(StatementTerminator),
 
             // Switch-specific stronger boundary
             Token::Keyword(Keyword::Case | Keyword::Default) => Some(SwitchArmStart),

rottlib/tests/parser_diagnostics/block_items.rs

@@ -0,0 +1,455 @@
+use super::*;
+
+pub(super) const P0025_FIXTURES: &[Fixture] = &[
+    Fixture {
+        label: "files/P0025_01.uc",
+        source: "{\n    local int Count;\n    Count = Count + 1 UpdateHud();\n    DrawHud(CanvasRef);\n}\n",
+    },
+    Fixture {
+        label: "files/P0025_02.uc",
+        source: "{\n    local float XL;\n    C.TextSize(LevelTitle, XL, YL)\n    C.SetPos(0, 0);\n    C.DrawText(LevelTitle);\n}\n",
+    },
+    Fixture {
+        label: "files/P0025_03.uc",
+        source: "{\n    local bool bReady;\n    bReady = CheckReady()\n    if (bReady) { StartMatch(); }\n    NotifyReady();\n}\n",
+    },
+    Fixture {
+        label: "files/P0025_04.uc",
+        source: "{\n    local int I;\n    Scores[I] = Scores[I] + 1\n    I++;\n    RefreshScores();\n}\n",
+    },
+];
+
+pub(super) const P0026_FIXTURES: &[Fixture] = &[
+    Fixture {
+        label: "files/P0026_01.uc",
+        source: "{\n    local int Count;\n    Count = 0;\n    Count++;\n    UpdateHud();\n",
+    },
+    Fixture {
+        label: "files/P0026_02.uc",
+        source: "{\n    local bool bReady;\n    bReady = CheckReady();\n    if (bReady) { StartMatch(); }\n    NotifyReady();\n",
+    },
+    Fixture {
+        label: "files/P0026_03.uc",
+        source: "{    local float XL;    do { C.TextSize(LevelTitle, XL, YL); } until (XL < C.ClipX)    C.SetPos(0, 0);    C.DrawText(LevelTitle);",
+    },
+    Fixture {
+        label: "files/P0026_04.uc",
+        source: "{\n    local int Count;\n    Count = Count + 1;\n    UpdateHud();\n    Count\n",
+    },
+];
+
+pub(super) const P0025_P0026_MIXED_FIXTURES: &[Fixture] = &[
+    Fixture {
+        label: "files/P_mixed_01.uc",
+        source: "{    local int Count;    Count = Count + 1    UpdateHud();    DrawHud(CanvasRef);",
+    },
+    Fixture {
+        label: "files/P_mixed_02.uc",
+        source: "{\n    local bool bReady;\n    bReady = CheckReady()\n    if (bReady) { StartMatch(); }\n    NotifyReady();\n",
+    },
+];
+
+#[test]
+fn check_p0025_fixtures() {
+    let runs = run_fixtures(P0025_FIXTURES);
+
+    assert_eq!(runs.get("files/P0025_01.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0025_02.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0025_03.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0025_04.uc").unwrap().len(), 1);
+
+    assert_diagnostic(
+        &runs.get_any("files/P0025_01.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `;` after expression statement",
+            severity: Severity::Error,
+            code: Some("P0025"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(21),
+                    end: TokenPosition(21),
+                },
+                message: "expected `;` before `UpdateHud`",
+            }),
+            secondary_labels: &[ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(11),
+                    end: TokenPosition(19),
+                },
+                message: "expression statement",
+            }],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0025_02.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `;` after expression statement",
+            severity: Severity::Error,
+            code: Some("P0025"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(25),
+                    end: TokenPosition(25),
+                },
+                message: "expected `;` before `C`",
+            }),
+            secondary_labels: &[ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(22),
+                    end: TokenPosition(22),
+                },
+                message: "expression statement ends here",
+            }],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0025_03.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `;` after expression statement",
+            severity: Severity::Error,
+            code: Some("P0025"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(20),
+                    end: TokenPosition(20),
+                },
+                message: "expected `;` before `if`",
+            }),
+            secondary_labels: &[ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(17),
+                    end: TokenPosition(17),
+                },
+                message: "expression statement ends here",
+            }],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0025_04.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `;` after expression statement",
+            severity: Severity::Error,
+            code: Some("P0025"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(28),
+                    end: TokenPosition(28),
+                },
+                message: "expected `;` before `I`",
+            }),
+            secondary_labels: &[ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(25),
+                    end: TokenPosition(25),
+                },
+                message: "expression statement ends here",
+            }],
+            help: None,
+            notes: &[],
+        },
+    );
+}
+
+#[test]
+fn check_p0026_fixtures() {
+    let runs = run_fixtures(P0026_FIXTURES);
+
+    assert_eq!(runs.get("files/P0026_01.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0026_02.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0026_03.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0026_04.uc").unwrap().len(), 1);
+
+    assert_diagnostic(
+        &runs.get_any("files/P0026_01.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `}` to close block",
+            severity: Severity::Error,
+            code: Some("P0026"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(0),
+                    end: TokenPosition(29),
+                },
+                message: "expected `}` before end of file",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0026_02.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `}` to close block",
+            severity: Severity::Error,
+            code: Some("P0026"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(0),
+                    end: TokenPosition(42),
+                },
+                message: "expected `}` before end of file",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0026_03.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `}` to close block",
+            severity: Severity::Error,
+            code: Some("P0026"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(59),
+                    end: TokenPosition(59),
+                },
+                message: "expected `}` before end of file",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0026_04.uc"),
+        &ExpectedDiagnostic {
+            headline: "missing `}` to close block",
+            severity: Severity::Error,
+            code: Some("P0026"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(0),
+                    end: TokenPosition(31),
+                },
+                message: "expected `}` before end of file",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+}
+
+#[test]
+fn check_p0025_mixed_fixtures() {
+    let runs = run_fixtures(P0025_P0026_MIXED_FIXTURES);
+
+    assert_eq!(runs.get("files/P_mixed_01.uc").unwrap().len(), 2);
+    assert_eq!(runs.get("files/P_mixed_02.uc").unwrap().len(), 2);
+
+    assert_diagnostic(
+        &runs.get_by_code("files/P_mixed_01.uc", "P0025"),
+        &ExpectedDiagnostic {
+            headline: "missing `;` after expression statement",
+            severity: Severity::Error,
+            code: Some("P0025"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(19),
+                    end: TokenPosition(19),
+                },
+                message: "expected `;` before `UpdateHud`",
+            }),
+            secondary_labels: &[ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(9),
+                    end: TokenPosition(17),
+                },
+                message: "expression statement",
+            }],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_by_code("files/P_mixed_02.uc", "P0025"),
+        &ExpectedDiagnostic {
+            headline: "missing `;` after expression statement",
+            severity: Severity::Error,
+            code: Some("P0025"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(20),
+                    end: TokenPosition(20),
+                },
+                message: "expected `;` before `if`",
+            }),
+            secondary_labels: &[ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(17),
+                    end: TokenPosition(17),
+                },
+                message: "expression statement ends here",
+            }],
+            help: None,
+            notes: &[],
+        },
+    );
+}
+
+#[test]
+fn check_p0026_mixed_fixtures() {
+    let runs = run_fixtures(P0025_P0026_MIXED_FIXTURES);
+
+    assert_eq!(runs.get("files/P_mixed_01.uc").unwrap().len(), 2);
+    assert_eq!(runs.get("files/P_mixed_02.uc").unwrap().len(), 2);
+
+    assert_diagnostic(
+        &runs.get_by_code("files/P_mixed_01.uc", "P0026"),
+        &ExpectedDiagnostic {
+            headline: "missing `}` to close block",
+            severity: Severity::Error,
+            code: Some("P0026"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(29),
+                    end: TokenPosition(29),
+                },
+                message: "expected `}` before end of file",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_by_code("files/P_mixed_02.uc", "P0026"),
+        &ExpectedDiagnostic {
+            headline: "missing `}` to close block",
+            severity: Severity::Error,
+            code: Some("P0026"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(0),
+                    end: TokenPosition(41),
+                },
+                message: "expected `}` before end of file",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+}
+
+pub(super) const P0027_FIXTURES: &[Fixture] = &[
+    Fixture {
+        label: "files/P0027_01.uc",
+        source: "{\n    local bool bReady;\n    bReady = CheckReady();\n    else { StartMatch(); }\n    NotifyReady();\n}\n",
+    },
+    Fixture {
+        label: "files/P0027_02.uc",
+        source: "{    local int Count;    Count = 3;    case 3:        Count++;    UpdateHud();}",
+    },
+    Fixture {
+        label: "files/P0027_03.uc",
+        source: "{\n    local bool bDone;\n    bDone = false;\n    until (bDone)\n    TickWork();\n}\n",
+    },
+    Fixture {
+        label: "files/P0027_04.uc",
+        source: "{\n    local int Count;\n    Count = 0;\n    #exec TEXTURE IMPORT NAME=Bad FILE=Bad.bmp\n    Count++;\n}\n",
+    },
+];
+
+#[test]
+fn check_p0027_fixtures() {
+    let runs = run_fixtures(P0027_FIXTURES);
+
+    assert_eq!(runs.get("files/P0027_01.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0027_02.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0027_03.uc").unwrap().len(), 1);
+    assert_eq!(runs.get("files/P0027_04.uc").unwrap().len(), 1);
+
+    assert_diagnostic(
+        &runs.get_any("files/P0027_01.uc"),
+        &ExpectedDiagnostic {
+            headline: "expected statement or expression, found `else`",
+            severity: Severity::Error,
+            code: Some("P0027"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(21),
+                    end: TokenPosition(21),
+                },
+                message: "unexpected `else`",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0027_02.uc"),
+        &ExpectedDiagnostic {
+            headline: "expected statement or expression, found `case`",
+            severity: Severity::Error,
+            code: Some("P0027"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(16),
+                    end: TokenPosition(16),
+                },
+                message: "unexpected `case`",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0027_03.uc"),
+        &ExpectedDiagnostic {
+            headline: "expected statement or expression, found `until`",
+            severity: Severity::Error,
+            code: Some("P0027"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(19),
+                    end: TokenPosition(19),
+                },
+                message: "unexpected `until`",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+
+    assert_diagnostic(
+        &runs.get_any("files/P0027_04.uc"),
+        &ExpectedDiagnostic {
+            headline: "expected statement or expression, found `#exec` directive",
+            severity: Severity::Error,
+            code: Some("P0027"),
+            primary_label: Some(ExpectedLabel {
+                span: TokenSpan {
+                    start: TokenPosition(19),
+                    end: TokenPosition(19),
+                },
+                message: "`#exec` directives are not allowed in a statement block",
+            }),
+            secondary_labels: &[],
+            help: None,
+            notes: &[],
+        },
+    );
+}

rottlib/tests/parser_diagnostics/mod.rs

@@ -5,6 +5,7 @@ use rottlib::diagnostics::{Diagnostic, Severity};
 use rottlib::lexer::{TokenPosition, TokenSpan, TokenizedFile};
 use rottlib::parser::Parser;
 
+mod block_items;
 mod control_flow_expressions;
 mod primary_expressions;